The present invention relates generally to the field of electrosurgery and, more particularly, to surgical devices and methods that employ high frequency electrical energy to increase the flow of blood to a target tissue.
Coronary artery disease, the build up of atherosclerotic plaque on the inner walls of the coronary arteries, causes the narrowing or complete closure of these arteries resulting in insufficient blood flow to the heart. A number of approaches have been developed for treating coronary artery disease. In less severe cases, it is often sufficient to treat the symptoms with pharmaceuticals and lifestyle modification to lessen the underlying causes of the disease. In more severe cases a coronary artery blockage can often be treated using endovascular techniques, such as balloon angioplasty, laser recanalization, placement of stents, and the like.
In cases where pharmaceutical treatment and endovascular approaches have failed or are likely to fail, it is often necessary to perform a coronary artery bypass graft (CABG) procedure using open or thoracoscopic surgical methods. For example, many patients still require bypass surgery due to such conditions as the presence of extremely diffuse stenotic lesions, the presence of total occlusions and the presence of stenotic lesions in extremely tortuous vessels. However, some patients are too sick to successfully undergo bypass surgery. For other patients, previous endovascular and/or bypass surgery attempts have failed to provide adequate revascularization of the heart muscle.
Laser myocardial revascularization (LMR) is a recent procedure developed with the recognition that myocardial circulation occurs through arterioluminal channels and myocardial sinusoids in the heart wall, as well as through the coronary arteries. In LMR procedures, artificial channels are formed in the myocardium with laser energy to provide blood flow to ischemic heart muscles by utilizing the heart""s ability to perfuse itself from these artificial channels through the arterioluminal channels and myocardial sinusoids. In one such procedure, a CO2 laser is utilized to vaporize tissue and produce channels in the heart wall from the epicardium through the endocardium to promote direct communication between blood within the ventricular cavity and that of existing myocardial vasculature. The laser energy is typically transmitted from the laser to the epicardium by an articulated arm device. Recently, a percutaneous method of LMR has been developed in which an elongated flexible laser apparatus is attached to a catheter and guided endoluminally into the patient""s heart. The inner wall of the heart is irradiated with laser energy to form a channel from the endocardium into the myocardium for a desired distance.
While recent techniques in LMR have been promising, they also suffer from a number of drawbacks inherent with laser technology. One such drawback is that the laser energy must be sufficiently concentrated to form channels through the heart tissue, which reduces the diameter of the channels formed by LMR. In addition, free beam lasers generally must completely form each artificial lumen or revascularizing channel during the still or quiescent period of the heart beat. Otherwise, the laser beam will damage surrounding portions of the heart as the heart beats and thus moves relative to the laser beam. Consequently, the surgeon must typically form the channel in less than about 0.08 seconds, which requires a relatively large amount of energy. This further reduces the size of the channels that may be formed with a given amount of laser energy. Applicant has found that the diameter or minimum lateral dimension of these artificial channels may have an effect on their ability to remain open. Thus, the relatively small diameter channels formed by existing LMR procedures (typically on the order of about 1 mm or less) may begin to close after a brief period of time, which reduces the blood flow to the heart tissue.
Another drawback with current LMR techniques is that it is difficult to precisely control the location and depth of the channels formed by lasers. For example, the speed in which the revascularizing channels are formed often makes it difficult to determine when a given channel has pierced the opposite side of the heart wall. In addition, the distance to which the laser beam extends into the heart tissue is difficult to control, which can lead to laser irradiation with heating or vaporization of blood or heart tissue within the ventricular cavity. For example, when using the LMR technique in a pericardial approach (i.e., from the outside surface of the heart to the inside surface), the laser beam may not only pierce through the entire wall of the heart but may also irradiate blood within the heart cavity. As a result, one or more blood thromboses or clots may be formed which can lead to vascular blockages elsewhere in the circulatory system. Alternatively, when using the LMR technique in an endocardial approach (i.e., from the inside surface of the heart toward the outside surface), the laser beam may not only pierce the entire wall of the heart but may also irradiate and damage tissue surrounding the outer boundary of the heart.
The promotion of blood flow to tissue, e.g., via canalization, vascularization or revascularization, is desirable in areas of the body other than the heart. The degenerative changes in the musculoskeletal system can be attributed to aging, trauma, overuse, and diminished focal blood supply. Degenerative changes of the musculoskeletal system are ubiquitous, particularly in the shoulder, knee, elbow, or the like. Conditions such as rotator cuff tendinitis, patellar tendinitis, tennis elbow, and plantar fasciitis are extremely common, and yet have no well-defined minimally invasive treatment protocol. Typically, the treatment consists of physical therapy, non-steroidal anti-inflammatories, and occasionally surgery. Recently in Europe, surgeons have begun using lithotrypsy, receiving only equivocal results.
One example of an area of the body that would benefit from vascularization is the meniscus tissue. The meniscus tissue, a C-shaped piece of fibrocartilage located at the peripheral aspect of the joint, typically has very little blood supply (particularly the inner portions of the meniscus). For that reason, when damaged, the meniscus is unable to undergo the normal healing process that occurs in most other tissues of the body. In addition, with age, the meniscus begins to deteriorate, often developing degenerative tears. Typically, when the meniscus is damaged, the torn pieces begins to move in an abnormal fashion inside the joint. Because the space between the bones of the joint is very small, as the abnormally mobile piece of meniscal tissue (meniscal fragment) moves, it may become caught between the bones of the joint (femur and tibia). When this happens, the knee becomes painful, swollen and difficult to move.
Another example of an area of the body that would benefit from vascularization is the tendons. When a tendon is damaged, the tendon usually forms tiny tears which allow collagen to leak from the injured areas. The collagen leakage causes inflammation of the tendon that can cut off the flow of blood and pinch the surrounding nerves. Because tendons are inherently poorly vascularized, and receive less oxygen, nutrients, and blood flow, as compared with other tissues and organs, tendons tend to heal much more slowly than other tissues of the body. Accordingly, there is a need for apparatus and methods to canalize, vascularize, revascularize, and/or increase blood flow to tendons that have been torn or otherwise damaged, so as to stimulate, expedite, or facilitate the healing process.
The present invention provides systems, apparatus and methods for selectively applying electrical energy to structures within or on the surface of a patient""s body. The systems, apparatus, and methods of the present invention are particularly useful for treating acute and chronic musculoskeletal or neurological injuries and disorders, such as strains, sprains, tendinitis, fasciitis, arthritis, bursitis and tenosynovitis. In particular, the systems and methods of the present invention are useful for increasing blood flow to a target tissue, by canalization of tissue, stimulating the body""s wound healing responses, such as inducing vascularization of tissue, stimulating collagen growth, altering cellular function, or other metabolic or physiologic events that promote healing and regeneration of injured tissue.
Systems and apparatus according to the present invention generally include an electrosurgical probe or catheter having a shaft with proximal and distal ends, one or more active electrode(s) at the distal end, and one or more connectors for coupling the active electrode(s) to a source of high frequency electrical energy. The distal end portion of the shaft will usually have a diameter of less than 3 mm, preferably less than 1 mm. The active electrode(s) are preferably supported within an electrically insulating support member typically formed of an inorganic material, such as a ceramic, a silicone rubber, or a glass.
In one method of the present invention, an active electrode is positioned in close proximity to tissue at a target site, and a high frequency voltage difference is applied between an active electrode and a return electrode to volumetrically remove or ablate tissue at the target site. The active electrode(s) may be translated or otherwise moved relative to the body structure during or after the application of electrical energy to form a void within the body structure, such as a hole, channel, stripe, crater, divot, surface damage, or the like. In some embodiments, the active electrode(s) are axially moved toward the body structure to volumetrically remove one or more channel(s), divot(s) or hole(s) through a portion of the structure. In other embodiments, the active electrode(s) are moved across the body structure to remove one or more stripe(s) or channel(s) of tissue. In most embodiments, electrically conductive fluid, such as isotonic saline, is located between the active electrode(s) and the body structure. In the bipolar modality, the conductive fluid generates a current flow path between the active electrode(s) and one or more return electrode(s). High frequency voltage is then applied between the active electrode(s) and the return electrode(s) through the current flow path created by the electrically conductive fluid.
In one aspect of the invention, a method is provided for vascularization or revascularization of a tendon, ligament, or meniscus. The present invention may be useful for acute muscle or tendon injury, iliotibial band syndrome, tendinitis, fasciitis, bursitis, tenosynovitis, strains, sprains and the like. In one embodiment of the present invention, artificial channels, holes, craters, or lumens are created during this procedure to vascularize the tendon and/or facilitate the healing process. In another embodiment, sufficient RF energy is applied to the tendon to vascularize a region around the target site without creating a hole, channel, crater or the like, in the tendon. According to the present invention, one or more active electrodes can be positioned adjacent to the tendon, and a voltage applied between the active electrode(s) and one or more return electrode(s). In an exemplary configuration, a high frequency voltage heats, damages, and/or ablates, (i.e. volumetrically removes) at least a portion of the tissue to be treated. The active electrode(s) can be advanced axially into the space vacated by the removed tissue to bore a channel through the tissue.
In one specific configuration, a void, hole, or crater is formed in the tendon by molecular dissociation or disintegration of tissue components. In these embodiments, the high frequency voltage applied to the active electrode(s) is sufficient to vaporize an electrically conductive fluid (e.g., a gel or isotonic saline) between the active electrode(s) and the tissue. Within the vaporized fluid, an ionized plasma is formed and charged particles (e.g., electrons) cause the molecular breakdown or disintegration of the tissue, perhaps to a depth of several cell layers. This molecular dissociation of tissue components is accompanied by the volumetric removal of the tissue. This process can be precisely controlled to effect the volumetric removal of tissue to a depth in the range of from about 10 microns to 150 microns, with minimal heating of, or damage to, surrounding or underlying tissue. A more complete description of this phenomenon is described in commonly assigned U.S. Pat. No. 5,683,366, the complete disclosure of which is incorporated by reference herein.
One of the advantages of the present invention, particularly over previous methods involving lasers, is that the surgeon can more precisely control the location, depth, and diameter of the vascularizing channels formed in the tissue. The ability to precisely control the volumetric removal of tissue results in a field of tissue ablation or removal that is very defined, consistent, and predictable. This precise control of tissue treatment also helps to minimize, or completely eliminate, damage to healthy tissue structures, such as muscles, cartilage, bone, and/or nerves, which may be adjacent to the target tissue. In addition, any severed blood vessels at the target site may be simultaneously cauterized and sealed as the tissue is removed to continuously maintain hemostasis during the procedure. This increases the surgeon""s field of view, and expedites the procedure. In one embodiment, the active electrode can remain in contact with the tendon tissue as the high frequency voltage ablates this tissue (or at least substantially close to the tissue, e.g., usually on the order of about 0.1 mm to 2.0 mm, and preferably about 0.1 mm to 1.0 mm). This preserves tactile sense and allows the surgeon to more accurately determine when to terminate cutting of a given channel so as to minimize damage to surrounding tissues and/or to minimize bleeding.
In open procedures, or in procedures in xe2x80x9cdryxe2x80x9d fields, the apparatus may further include a fluid delivery element for delivering electrically conductive fluid to the active electrode(s) and the target site. The fluid delivery element may be located on the probe, e.g., in the form of a fluid lumen or tube, or it may be part of a separate instrument. In arthroscopic procedures, however, the surgical area surrounding the tendon will typically be filled with electrically conductive fluid (e.g., isotonic saline) so that the apparatus need not have a fluid delivery element. In both embodiments, the electrically conductive fluid will preferably generate a current flow path between the active electrode(s) and one or more return electrode(s). In an exemplary embodiment, the return electrode is located on the probe and spaced a sufficient distance from the active electrode(s) to substantially avoid or minimize current shorting therebetween and to shield the return electrode from tissue at the target site.
According to one aspect of the invention, there is provided an electrosurgical system including a probe having a shaft and an electrode assembly disposed on the shaft; an arthroscope for passing at least a distal end portion of the shaft therethrough; and a sensing unit adapted for determining a boundary of a target tissue. The sensing unit may include an element, such as an ultrasonic transducer, located on the shaft distal end, and an ultrasonic generator. The system may further include an adjustable mechanical stop for limiting the maximum travel of the shaft within a target tissue. The electrode assembly typically includes at least one active electrode and a return electrode. The system further includes a high frequency power supply for applying a high frequency voltage between the active and return electrodes. In one embodiment, the sensing unit may be coupled to the power supply, and the system configured to shut off power from the power supply according to a location of the shaft distal end in relation to a target tissue.
In one aspect, the invention provides a method for treating a damaged or poorly vascularized tissue, such as a meniscus of a joint, or a tendon. In one embodiment one or more channels or voids are formed in a target tissue via selective electrosurgical ablation of the tissue. One or more implants may be inserted in the one or more channels. In one embodiment, at least one channel bridges a lesion in the target tissue, and an implant inserted in the channel serves as a splint. In another embodiment, an implant is inserted in a channel to maintain patency in the channel, the channel serving as a conduit for blood flow within the target tissue, and the implant serving as a stent. In a further embodiment, an implant is inserted in a channel to promote hemostasis of the channel. In yet another embodiment, a stent is inserted in a distal portion of a channel, and a hemostasis plug is inserted in a proximal portion of the channel.
In another aspect, the invention provides a method for increasing blood flow to a target tissue by eliciting a wound healing response in the target tissue. In one embodiment, the wound healing response is elicited by the controlled application of heat thereto. Typically, the target tissue is heated using an electrosurgical probe to deliver high frequency, or radio frequency (RF), electrical energy thereto. Usually, the target tissue is heated to a temperature less than about 150xc2x0 C.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the accompanying drawings.